/*
 * @(#)MD5InputStream.java   0.3-3 06/05/2001
 *
 *  This file is part of the HTTPClient package
 *  Copyright (C) 1996-2001 Ronald Tschal�r
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307, USA
 *
 *  For questions, suggestions, bug-reports, enhancement-requests etc.
 *  I may be contacted at:
 *
 *  ronald@innovation.ch
 *
 *  The HTTPClient's home page is located at:
 *
 *  http://www.innovation.ch/java/HTTPClient/ 
 *
 */

package org.everrest.http.client;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * This class calculates a running md5 digest of the data read. When the stream
 * is closed the calculated digest is passed to a HashVerifier which is expected
 * to verify this digest and to throw an Exception if it fails.
 * 
 * @version 0.3-3 06/05/2001
 * @author Ronald Tschal�r
 */
class MD5InputStream extends FilterInputStream
{
   private HashVerifier verifier;

   private MessageDigest md5;

   private long rcvd = 0;

   private boolean closed = false;

   /**
    * @param is the input stream over which the md5 hash is to be calculated
    * @param verifier the HashVerifier to invoke when the stream is closed
    */
   public MD5InputStream(InputStream is, HashVerifier verifier)
   {
      super(is);
      this.verifier = verifier;
      try
      {
         md5 = MessageDigest.getInstance("MD5");
      }
      catch (NoSuchAlgorithmException nsae)
      {
         throw new Error(nsae.toString());
      }
   }

   public synchronized int read() throws IOException
   {
      int b = in.read();
      if (b != -1)
         md5.update((byte)b);
      else
         real_close();

      rcvd++;
      return b;
   }

   public synchronized int read(byte[] buf, int off, int len) throws IOException
   {
      int num = in.read(buf, off, len);
      if (num > 0)
         md5.update(buf, off, num);
      else
         real_close();

      rcvd += num;
      return num;
   }

   public synchronized long skip(long num) throws IOException
   {
      byte[] tmp = new byte[(int)num];
      int got = read(tmp, 0, (int)num);

      if (got > 0)
         return (long)got;
      else
         return 0L;
   }

   /**
    * Close the stream and check the digest. If the stream has not been fully
    * read then the rest of the data will first be read (and discarded) to
    * complete the digest calculation.
    * 
    * @exception IOException if the close()'ing the underlying stream throws an
    *            IOException, or if the expected digest and the calculated
    *            digest don't match.
    */
   public synchronized void close() throws IOException
   {
      while (skip(10000) > 0);
      real_close();
   }

   /**
    * Close the stream and check the digest.
    * 
    * @exception IOException if the close()'ing the underlying stream throws an
    *            IOException, or if the expected digest and the calculated
    *            digest don't match.
    */
   private void real_close() throws IOException
   {
      if (closed)
         return;
      closed = true;

      in.close();
      verifier.verifyHash(md5.digest(), rcvd);
   }
}
